1. Field of the Invention
The present invention relates to a vacuum fluorescent display. More particularly, the present invention relates to a power-economy vacuum fluorescent display which alternately powers filaments to emanate electrons therefrom in the manner of a scanning operation and thus reduces the overall power dissipation.
2. Description of the Related Art
With the characteristics of bright-color and great brightness, vacuum fluorescent displays have been widely applied to household appliance indicator panels and automobile instrument panels as well. Referring to FIG. 1, a schematic diagram of a vacuum fluorescent display is depicted. The operation of the vacuum fluorescent display will be described in conjunction with FIG. 1 as follows.
As shown in FIG. 1, reference numeral 1 designates a filament which is connected to and powered by a DC or AC power supply for inducing hot-electron emanation as an electron source. Although only one filament 1 is illustrated, a plurality of filaments should be provided for furnishing sufficient electrons. Reference numeral 2 designates a grid generally powered by a positive voltage to accelerate the generated electrons and confine their progress paths within a predetermined range. Reference numeral 3 represents a display portion, which comprises seven segmented anodes 3A, 3B, 3C, 3D, 3E, 3F, and 3G as shown in FIG. 1. These anodes 3A-3G, with a fluorescent material coated thereon, will emit fluorescent light when electrons collide with the surface of the anodes 3A-3G. Reference numeral 4 designates a plurality of data lines connected to the respective segmented anode 3A, 3B, 3C, 3D, 3E, 3F, or 3G. If any anode 3A, 3B, 3C, 3D, 3E, 3F, or 3G is desired to emit fluorescent light, a positive voltage is applied to the corresponding data line 4. To the contrary, a negative voltage will be applied to the corresponding data line 4 when the controlled anode 3A, 3B, 3C, 3D, 3E, 3F, or 3G is not intended to emit fluorescent light. For example, to display a digit "3", the anodes 3B, 3C, 3D, 3F, and 3G are powered by positive voltages while the anodes 3A and 3E are powered by negative voltages, through the associated data lines 4.
Typically, of the vacuum fluorescent display simultaneously powers every filament at all time during operation, which is estimated to consume three-fourth of overall power dissipation. While power dissipation is not so much of an issue in the application of vacuum fluorescent displays to household appliance indicator panels and automobile instrument panels, low power consumption can offer better competitiveness and also adhere to the current trend towards energy resource conservation. Moreover, in the application of vacuum fluorescent displays to portable products such as cellular phones, high power dissipation consumed by the filaments is unfavorable.